Pumps pervade industry. They are used to transfer fluids for every imaginable use, and to raise or lower the fluid pressure as appropriate. The common factor in all pumping is that there is a suction, or low-pressure, zone on the inlet side and a compression, or high-pressure, zone on the outlet side. On the outlet side, the fluid may pass on to another destination, or it may be a waste stream that is discharged.
The fluid stream passing through the pump may be gas or liquid. Gas emissions from pumps are often contaminated with vapors whose release to the atmosphere is environmentally undesirable or unacceptable, such as hydrocarbons, aromatic hydrocarbons, chlorinated hydrocarbons, fluorinated hydrocarbons, ammonia, sulfur dioxide or hydrogen sulfide. Likewise, when the outlet stream from the pump is to be passed to some other operation, not vented, it may contain vapor impurities the removal of which from the stream would be advantageous.
An undesirable component may be present in the gas on the inlet side of the pump, or it may be picked up as the gas goes through the pump. One specific instance of this is when the pump is a liquid-ring pump. In liquid-ring pumps, the pumping action is provided by a ring of liquid sealant or compressant. This ring may be water or some other liquid. The choice of liquid sealant is vast, including oils, hydrocarbons, chlorinated hydrocarbons, alcohols and inorganic liquids. Depending on vapor pressure and other factors, some sealant vapor will always be present in the outlet gas.
No cheap, reliable technology exists to treat pump outlet streams to an adequate level. Many pumps are already equipped with an external condenser that treats the exit stream to remove pollutants. Nevertheless, there is a practical limit, usually set by the process economics, on the amount of the pollutant that can be removed. There remains a need for economical ways of reducing the pollution caused by pump emissions, and for treating internal process streams passing through pumps.